Identifying Inertial Modes in a Hide-Titman Flow

Mary T. Catalano, University of Dallas

Advisors: Professor Daniel Lathrop, Don Martin, Dr. Daniel Zimmerman

Inertial modes are internal wave patterns present within a bounded, rotating fluid being restored by the Coriolis force. Hide and Titman1 found that a cylindrical container filled with homogeneous liquid and having a thin disk mounted coaxially inside of it will display nonaxisymmetric fluid flow when the differential rotation between the cylinder and the disk exceeds a critical threshold. Their essential geometry and setup were replicated and the fluid flow produced was analyzed to ascertain its relationship, if any, to the inertial modes of the cylinder. Previously, the inertial modes for this geometry had been expressed in analytical form by Zhang, et al.2 Seeking to correlate observed fluid flows with inertial modes contributes to a broader understanding of rotational fluid behavior.

Saara A. Khan, University of Maryland College Park

To meet future demands of free electron lasers, reliable and long-lasting photcathodes must be produced. With current photocathodes lacking qualities of both lifetime and high quantum efficiency, research continues to explore ways to formulate a desired photocathode. In this work, gold is deposited onto a tungsten cathode and the quantum efficiency (QE) is measured as a function of submonolayer cesium coverage. Quantum efficiency and contamination characterization of evaporatively deposited metal cathodes such as gold opens possibilities for future controlled porosity insulating substrates. Comparison will be made to theoretical models for QE. Gold cathodes may also have better robustness to oxidizing gases than existing tungsten cathodes.

Magnetic Gradiometer for Breast Cancer Surgery

Divya Nithianandam, University of Maryland College Park

Advisor: Professor Wesley Lawson

The overall purpose of this project is to create a device which will aid in removal of cancerous tumors. In order to do this, a first-generation magnetic gradiometer has been developed which can locate implanted magnets in breast cancer tumors. This device is unreliable since there are many magnetic objects and varying magnetic fields in an operating room. The next generation device must calibrate and cancel the unwanted fields so that the device can locate the implant precisely. In order to achieve this, research and testing must be done to find the proper components, optimal geometry, placement of sensors, and calibration/initialization of unwanted fields. With thorough testing and simulation of the device and evaluation, the proper configuration of the device can be determined.

Analysis of Microwave Propagation in Plasma

Elaine Chung, Rice University

Advisor: Dr. John Rodgers

Since plasma can be controlled electronically, it would be a useful feedback mechanism in a high-powered backwards wave oscillator (BWO). A BWO with a feedback mechanism can demonstrate multifrequency operation, which has high-power microwave applications. However, before we can use plasma in a BWO, we must first study how microwaves propagate through plasma. In this project, we will analyze the reflection of microwaves through plasma while varying the plasma's drift velocity, electron density, and neutral gas density. The goal of this project is to develop a better understanding of how the various plasma properties affect microwave propagation.

Dictyostelium Discoideum Movement in Electric Fields

Eric Kim, University of Maryland

Advisors: Associate Professor Wolfgang Losert and Can Guven

Recent studies have shown that amoeboid cells respond to external electric fields by exhibiting migration towards the cathode. A deeper understanding of this phenomenon would facilitate research in wound healing, embryogenesis, and the dynamics of cancer cells. Our study used the amoeba Dictyostelium discoideum as a model organism and aims to analyze the ultimately control cell movement and membrane topology with a time-dependent electric field. In our investigation, we use a custom image analysis code to study cell movement and responses to external electric fields.

Wave Forcing in a Rotating Cylindrical Flow

Robert L. Blum, University of Maryland College Park
Mary T. Catalano, University of Dallas

Bounded rotating fluid flows exhibit linear wave modes known as inertial modes, which are restored by the Coriolis force. Recently, Kelley et al. have found that the strong inertial modes observed in their 60-cm spherical Couette experiment are excited by over-reflection, a process where waves are amplified by reflection from shear layers. Kelley et al. were not able to take direct velocity measurements. We seek similar behavior in a rotating cylinder with a differentially rotating, axis-aligned disk mounted in the center. Using particle image velocimetry to measure the flow very near the disk, we examine the interaction between the turbulent boundary layer near the disk and the bulk flow.

Random Number Generation Using Amplified Spontaneous Emission in a Fiber Amplifier

Julia Salevan, University of Maryland College Park

Random number generators (RNGs) have applications ranging from cryptography to Monte Carlo simulation and stochastic modeling. The goal of our research is to create a stable, fast physical RNG, using as our source the broadband optical noise from the amplified spontaneous emission in a fiber amplifier driven by a pump laser. We examined methods to achieve generation rates up to 12.5 Gh/s, including mixing our data with itself and with pseudo-random bitstreams. We analyzed our data using the NIST and Diehard batteries of tests for randomness and developed an automated program to characterize the statistics of the amplified spontaneous emission noise.

John Stout, North Carolina State
Matthew Whiteway, University of Oklahoma

Systems consisting of a large number of coupled oscillators commonly occur in science, technology, and particularly biology -- examples include the synchronization of flashing fireflies, pacemaker cells in the heart, and laser arrays. The Kuramoto model has been used extensively to model such systems, and we employ this model to study how different network parameters influence the dynamics of these systems. In particular, we investigate the effects that network size, topology, and the natural frequency distribution of the system have on the path to global synchronization as the overall coupling strength between oscillators is increased.

MHD Simulation of Flare Experiment

Jeffrey Kollasch, Iowa State University

Advisors: Professor James Drake and Dr. Marc Swisdak

Solar prominence eruptions are believed to be caused by a phenomenon called magnetic reconnection in which opposing magnetic field lines violently break and reconnect releasing stored magnetic energy into the surrounding plasma. Although much can be learned by observing natural reconnection events, recent progress is being made in dedicated laboratory experiments. One avenue of experiments is to create laboratory-scale expanding magnetic flux tubes in imitation of solar prominences. Presented here is a three-dimensional MHD computer simulation of such an experiment which may be used for finding optimal experimental conditions and also for comparison with the experimental data once obtained.